Climatological winter started on December 1 and the Valley has seen plenty of cold days since then. This is also the time that many people have to deal with one of the biggest consequences of cold air: dry skin. Have you ever wondered why your skin gets so dry during the winter? Let’s dig into the relationship between cold temperatures and dry air.

The simple answer is that there is a relationship between air temperature and moisture. When the air temperature becomes colder, the capacity for our atmosphere to hold water vapor decreases. Indeed, there is a direct relationship between air temperature and atmospheric water vapor content.

Conversely, the atmosphere has the potential for higher water vapor content when the temperature is higher. This is why humid conditions occur in the summer time when the air temperature is warmer.

This relationship affects the amount of precipitation that the atmosphere can produce, as well. We can explore this relationship visually. If we take the average temperature for each month and compare it to the average observed precipitation, then you can see this relationship. This is the data for the Youngstown/Warren Regional Airport:

Average temperature and observed precipitation for every month from the Youngstown/Warren Regional Airport. The temperature line goes from the purple color to yellow and the corresponding y-axis can be found on the left side of the graph. The precipitation line is green and the corresponding y-axis can be found on the right side of the graph.

Now, the relationship is not perfect, but you can see from the graph that higher monthly precipitation values are recorded during the summer months (June, July, and August) while lower monthly precipitation values are generally recorded during the winter months (December, January, February).

You have been educated on the relationship between temperature and water vapor. Now, I will set you free to use the knowledge as you see fit. Or, you can stick around and learn about a more technical explanation.

What in the world is the Clausius-Clapeyron equation?

If you have made it this far, then you are really interested in this subject and I commend you. I already explained that there is a relationship between atmospheric water vapor content and temperature. What is the exact reason for this?

Thankfully, most of the work is already done for us (something about standing on the shoulders of giants) and all I need to do is explain the physics behind this relationship.

A German scientist by the name of Rudolf Clausius and a french scientist by the name of Benoît Paul Émile Clapeyron were the creators of the Clausius-Calpeyron equation which states that there is a relationship between air temperature and the vapor pressure of a molecule.

What exactly is vapor pressure you ask? Well, if you think about pressure, you might think about a heavy weight on a table. If the object is heavy enough, then it might break the table due to the pressure. It turns out that water molecules also give off pressure, but on a much smaller scale.

When the temperature is cold, water molecules move around slower than they would if it were warm (just like you move slower during the winter months haha). If the temperature is warm, then the water molecules move at a faster speed which causes them to release more pressure.

The “pressure” in this case is actually more water vapor. Therefore, warmer temperatures make more water vapor available to the atmosphere than colder temperatures. If my explanation was not enough for you, then you can also watch a video on the topic that I have attached below.